Physiology of aging among healthy, older bottlenose dolphins (Tursiops truncatus): comparisons with aging humans.

Changes in hematological and serum chemistry values have been identified among older compared to younger humans. We hypothesized that healthy bottlenose dolphins (Tursiops truncatus) 30 years and older may demonstrate similar clinicopathological changes with increasing age. Retrospective hematological and serum chemistry data generated from routine, fasted blood samples collected over 10 to 20 years among six healthy dolphins that lived at least 40 years were analyzed to (1) assess linear trends in blood variable values with increasing age, (2) compare mean blood values by older age categories (30-35 years, 36-40 years, and >40 years), and (3) compare the prevalence of clinically high or low blood values by older age categories. Absolute lymphocytes, serum globulins, and mean platelet volume increased linearly with increasing old age. Mean white blood cells, neutrophils, serum globulins, erythrocyte sedimentation rates, serum cholesterol, and serum triglycerides; and the prevalence of neutrophilic leukocytosis, hyperglobulinemia, and hypercholesterolemia, were more likely to be higher as geriatric dolphins got older. A linear decrease in serum albumin with increasing age was present for five of six animals. Serum creatinine decreased among dolphins older than 40 years compared to when they were 30-40 years old. Our study demonstrates that older dolphins have changes in hematological and serum chemistry values similar to those found in older humans. As such, bottlenose dolphins may serve as a useful comparative model for aging in humans. Further studies are needed to assess whether these changes are associated with negative health outcomes and whether targeted therapeutics can help improve quality of life among aging dolphins.